This invention relates in general to an apparatus and a method of performed a hydroforming process on a workpiece so as to deform a workpiece to achieve a desired shape. In particular, this invention relates to an improved apparatus and method for performing such a hydroforming process wherein either or both of the opposed end portions of the workpiece are also deformed to achieve desired shapes therein.
Hydroforming is a well known process that uses pressurized fluid to deform a closed channel workpiece to a desired shape. A typical apparatus for performing a hydroforming process includes a frame having first and second die sections that are supported for movement relative to one another between opened and closed positions. The first and second die sections have respective recesses formed therein that together define a die cavity having a shape that corresponds to a desired final shape for the workpiece. When moved to the opened position, the first and second die sections are spaced apart from one another to allow a workpiece to be inserted within the die cavity. When moved to the closed position, the die sections engage one another to enclose the workpiece within the die cavity. Although the die cavity is usually somewhat larger than the workpiece to be hydroformed, movement of the two die sections from the opened position to the closed position may, in some instances, cause some mechanical deformation of the workpiece. In any event, the workpiece is then filled with fluid, typically a relatively incompressible liquid such as water. Fluid pressure within the workpiece is increased to such a magnitude that the workpiece is deformed outwardly into conformance with the surface contour of the die cavity. As a result, the workpiece is deformed into the desired final shape.
In a typical hydroforming apparatus, the die sections are arranged such that the first die section is supported on a movable ram of the apparatus, while the second die section is supported on a stationary bed of the apparatus. A mechanical or hydraulic actuator is provided for moving the ram and the first die section to the opened position relative to the second die section, allowing a previously deformed workpiece to be removed from the die cavity and a new workpiece to be inserted within the die cavity. The actuator subsequently moves the ram and the first die section to the closed position relative to the second die section, allowing the hydroforming process to be performed. To maintain the die sections together during the hydroforming process, a clamping or retaining device may be provided. The clamping or retaining device mechanically engages the die sections (or, alternatively, the ram and the base upon which the die sections are supported) to prevent them from moving apart from one another during the hydroforming process. Such movement would obviously be undesirable because the shape of the die cavity would become distorted, resulting in undesirable variations in the final shape of the workpiece.
In order to facilitate the filling of the workpiece with fluid and the subsequent performance of the hydroforming process, the hydroforming apparatus is typically provided with a pair of end feed assemblies. The end feed assemblies are adapted to engage and seal against opposed end portions of the workpiece that protrude from the sides of the hydroforming die. Fluid can then be fed into the workpiece through either or both of the end feed assemblies to perform the hydroforming process. Additionally, the end feed assemblies can be used to exert forces axially inwardly against the opposed end portions of the workpiece during the hydroforming process. As a result, some of the material from the end portions of the workpiece is pushed within the hydroforming die as the interior portion of the workpiece is being deformed. This axial end feeding process minimizes the reduction in the wall thickness of the interior portion of the workpiece that otherwise might result during the hydroforming process. When the hydroforming process is completed, the end feed assemblies are disengaged from the opposed end portions of the workpiece to allow the workpiece to be removed from the hydroforming die.
Typically, the opposed end portions of the workpieces that are engaged by the end feed assemblies are generally hollow and cylindrical in shape. Such hollow cylindrical shape facilitates the engagement and sealing of the opposed end portions of the workpiece by the end feed assemblies, as described above. However, with known end feed assemblies, such opposed end portions of the workpiece are not deformed, either before, during, or after the hydroforming process. Thus, the opposed end portions of the workpiece remain in their original hollow and cylindrical shape after the hydroforming process is completed. Frequently, these hollow cylindrical end portions are not desired in the final hydroformed workpiece. Consequently, these hollow cylindrical end portions are typically removed from the hydroformed workpiece, such as by cutting, and discarded as scrap. Although this process has functioned satisfactorily, it has been found to be somewhat time consuming and wasteful. Thus, it would be desirable to provide an improved apparatus and method for performing a hydroforming process wherein either or both of the opposed end portions of the workpiece are also deformed to achieve desired shapes therein, thereby eliminating the need to remove and discard them.